U.S. patent number 8,034,267 [Application Number 11/625,370] was granted by the patent office on 2011-10-11 for composite solid tire and method of producing same.
This patent grant is currently assigned to Maeda Shell Service Co., Ltd.. Invention is credited to Sadao Maeda.
United States Patent |
8,034,267 |
Maeda |
October 11, 2011 |
Composite solid tire and method of producing same
Abstract
A composite solid tire, including a worn solid rubber tire
having a remaining rubber layer, and a thermo-setting polyurethane
elastomer layer which is provided on an outer circumferential
surface of the rubber layer.
Inventors: |
Maeda; Sadao (Okazaki,
JP) |
Assignee: |
Maeda Shell Service Co., Ltd.
(Okazaki-Shi, JP)
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Family
ID: |
34824560 |
Appl.
No.: |
11/625,370 |
Filed: |
January 22, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070114688 A1 |
May 24, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11060133 |
Feb 17, 2005 |
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Foreign Application Priority Data
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Mar 9, 2004 [JP] |
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2004-066104 |
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Current U.S.
Class: |
264/36.14;
156/404; 156/112; 264/319 |
Current CPC
Class: |
B60C
7/102 (20130101); B29D 30/06 (20130101); B60C
7/00 (20130101); B29D 30/02 (20130101); B60C
11/02 (20130101); B29D 30/54 (20130101); B60C
2007/005 (20130101); Y10T 152/10306 (20150115) |
Current International
Class: |
B29D
30/54 (20060101); B60C 7/00 (20060101) |
Field of
Search: |
;156/128.1,112,404
;264/36.14,319 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1062692 |
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Jul 1992 |
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CN |
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1460591 |
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Dec 2003 |
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CN |
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2755111 |
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Jun 1979 |
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DE |
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3711038 |
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Oct 1987 |
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DE |
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0157717 |
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Oct 1985 |
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EP |
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0 720 923 |
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Jul 1996 |
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EP |
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1 262 301 |
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Dec 2002 |
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EP |
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2264502 |
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Feb 1992 |
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GB |
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2 264 502 |
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Sep 1993 |
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GB |
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05-031822 |
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Feb 1993 |
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JP |
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2002-14442 |
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May 2002 |
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JP |
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WO 02/083782 |
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Oct 2002 |
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WO |
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Other References
US. Appl. No. 11/007,776, filed Dec. 8, 2004, Maeda. cited by other
.
Zhiping Lu, et al., "Synthesis of Polyurethane Elastomers Using
1,5-naphthalene Diisocyanate," Synthetic Rubber Industry, 19(3),
1996, pp. 185-187. cited by other.
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Primary Examiner: Crispino; Richard
Assistant Examiner: Rogers; Martin
Attorney, Agent or Firm: Burr & Brown
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. application Ser. No.
11/060,133, filed Feb. 17, 2005, which claims the benefit of
Japanese Patent Application No. 2004-066104, filed Mar. 9, 2004,
the entireties of which are incorporated herein by reference.
Claims
What is claimed is:
1. A method of producing a composite solid tire, comprising the
steps of providing a rubber layer to be an inner layer of said
tire; applying a primer and an adhesive to the outer
circumferential surface of said rubber layer; providing a
die-casting device including an outer die having a cylindrical
shape with a bottom; pre-heating the outer die and the rubber layer
individually, the outer die being heated to a temperature of
100.degree. C. to 110.degree. C. and the rubber layer being heated
to a temperature 5.degree. C. higher than that of the pre-heated
outer die; setting the pre-heated rubber layer and the preheated
outer die concentrically such that a casting space is formed
between an inner circumferential surface of the outer die and the
outer circumferential surface of the rubber layer; and introducing
raw materials of a thermo-setting polyurethane elastomer into the
casting space to react and cure, thereby integrally forming an
outer layer of the thermo-setting polyurethane elastomer.
2. The method of producing a composite solid tire according to
claim 1, wherein said rubber layer is formed of a worn solid rubber
tire, and the rubber layer has a pre-determined thickness.
3. The method of producing a composite solid tire according to
claim 1, wherein said rubber layer is formed of at least one rubber
material, which is softer than the thermo-setting polyurethane
elastomer of the outer layer.
4. The method of producing a composite solid tire according to
claim 1, wherein a characteristic value of the thereto-setting
polyurethane elastomer according to Taber Abrasion Test measured in
accordance with DIN 53516 is 90 mm.sup.3 or less.
5. The method of producing a composite solid tire according to
claim 1, wherein a percentage of a thickness of the outer layer
relative to a whole thickness of said composite solid tire in a
radial direction thereof is not more than 40%.
6. The method of producing a composite solid tire according to
claim 1, wherein said outer layer is formed by reacting and setting
of at least one polyisocyanate component selected from the group
consisting of tolylene diisocyanate (TDI), diphenylmethane
diisocyanate (MDI), and naphthalene diisocyanate (NDI), and at
least one polyol component selected from the group consisting of
poly(oxybutylene)glycol, polyester polyol, and polyethylene adipate
glycol.
7. The method of producing a composite solid tire according to
claim 6, wherein said at least one polyisocyanate component and
said at least one polyol component are reacted and set at a
temperature of 70.degree. C. to 115.degree. C.
8. A method of producing a composite solid tire, the method
comprising the steps of cutting an outer circumferential surface of
a remaining rubber layer of a worn solid rubber tire; applying a
primer and an adhesive to the cut outer circumferential surface of
the rubber layer; providing a die-casting device including an outer
die having a cylindrical shape with a bottom; pre-heating the outer
die and the rubber layer individually, the outer die being heated
to a temperature of 100.degree. C. to 110.degree. C. and the rubber
layer being heated to a temperature 5.degree. C. higher than that
of the pre-heated outer die; setting the pre-heated rubber layer
and the preheated outer die concentrically such that a casting
space is formed between an inner circumferential surface of the
outer die and the outer circumferential surface of the rubber
layer; and introducing raw materials of a thermo-setting
polyurethane elastomer into the casting space to react and cure,
thereby integrally forming an outer layer of the thermo-setting
polyurethane elastomer.
9. The method of producing a composite solid tire according to
claim 8, wherein said rubber layer is formed of a worn solid rubber
tire, and the rubber layer has a pre-determined thickness.
10. The method of producing a composite solid tire according to
claim 8, wherein said rubber layer is formed of at least one rubber
material, which is softer than the thermo-setting polyurethane
elastomer of the outer layer.
11. The method of producing a composite solid tire according to
claim 8, wherein a characteristic value of the thermo-setting
polyurethane elastomer according to Taber Abrasion Test measured in
accordance with DIN 53516 is 90 mm.sup.3 or less.
12. The method of producing a composite solid tire according to
claim 8, wherein a percentage of a thickness of the outer layer
relative to a whole thickness of said composite solid tire in a
radial direction thereof is not more than 40%.
13. The method of producing a composite solid tire according to
claim 8, wherein said outer layer is formed by reacting and setting
of at least one polyisocyanate component selected from the group
consisting of tolylene diisocyanate (TDI), diphenylmethane
diisocyanate (MDI), and naphthalene diisocyanate (NDI), and at
least one polyol component selected from the group consisting of
poly(oxybutylene)glycol, polyester polyol, and polyethylene adipate
glycol.
14. The method of producing a composite solid tire according to
claim 13, wherein said at least one polyisocyanate component and
said at least one polyol component are reacted and set at a
temperature of 70.degree. C. to 115.degree. C.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite solid tire and a
method of producing the same, and particularly to advantageous
techniques for renewing worn solid rubber tires.
2. Discussion of Related Art
As a tire that supports, in a vehicle such as an automotive vehicle
or an industrial vehicle, a load and has the function of smoothly
transmitting forces between the vehicle and road surface, there
have conventionally been known two sorts of tires, i.e., a
pneumatic tire having a hollow structure in which air is charged,
and a solid tire having a solid structure constituted by a
rubber-based annular body. In particular, the solid tire enjoys, as
tire's functions, a load supporting property, a cushioning
property, and a rubber elasticity, and is widely used in low-speed
and high-load vehicles such as a forklift truck, an industrial
tractor, a battery carrier, or a trailer. As predominant sorts of
the solid tire, there are known a tire that is constituted by a
single tread rubber and is directly bonded to a wheel, a tire that
is constituted by a rubber adhered, by vulcanization, to a base
band and is press-fitted onto a wheel, and a tire that is
constituted by an annular tread rubber and is fitted on an outer
circumferential portion of a wheel.
Generally, the solid tire is known as a solid rubber tire that is
constituted by a tread rubber formed of, e.g., NR or SBR. Since the
solid rubber tire contacts the road surface and produces a
frictional force to allow movement of the vehicle, a surface of
contact of the tire with the road surface is worn little by little
as the tire is used for a long time and, if a life expectancy of
the tire is fulfilled, the tire should be disposed of. Recently,
however, the disposal of waste tires has become a serious social
problem. In particular, since the solid rubber tires are heavier
than pneumatic tires used in, e.g., passenger cars, the solid
rubber tires are more difficult to handle. In addition, the solid
rubber tires are hard to burn or find other applications. Thus, the
solid rubber tires are very difficult to dispose of.
In the above-indicated technical background, Patent Document 1
(Japanese Patent Application Publication No. 5-31822) has proposed
a pneumatic-type solid tire having a structure in which a surface
of a tread portion of a worn tire is subjected to buffing as a sort
of polishing and a renewing tread rubber is adhered to the thus
polished tread portion. According to this technique, worn tires
that have conventionally been difficult to dispose of can be
effectively utilized, tire materials can be saved, and times needed
to produce tires can be reduced.
However, even though the renewing tread rubber may be adhered to
the tread portion of the worn tire, so as to produce a renewed
tire, the tread portion of the renewed tire is easily worn again as
it is used. Thus, the durability of the tread portion of the
renewed tire is not satisfactorily improved. In addition, since
rubber materials used to form the renewed tread rubber contain
carbon black as a reinforcing agent and accordingly have a black
color, black marks of the tire are left on the road surface because
frictions are produced between the tread rubber and the road
surface. The black tire marks left on the road surface may damage
an aesthetic appearance of the road surface and, in a work field
where a forklift truck or an industrial tractor is used, not only
the black tire marks but also black rubber powder resulting from
wearing of tires may damage a work environment.
In addition, Patent Document 2 (Japanese Patent Application
Publication No. 2002-144442) discloses a wheel renewing method in
which urethane rubber is used. More specifically described, this
document discloses a renewed wheel obtaining technique in which,
after a rubber portion is removed from a base band of a waste tire,
an ether-based urethane rubber layer is formed on an outer
circumferential surface of the base band.
In the above-indicated renewed wheel, the urethane rubber layer
contacts road surface. The urethane rubber has a higher wear
resistance than that of a common tread rubber formed of, e.g., NR
or SBR. Thus, the renewed wheel can enjoy a significantly improved
durability or life expectancy. On the other hand, the renewed wheel
suffers a lower cushioning property than that of a wheel having the
common tread rubber. Therefore, when an operator operates a
vehicle, such as a forklift truck or an industrial tractor, in
which the renewed wheel is used, uncomfortable shocks may be
transmitted to the operator. The cushioning property of the renewed
wheel might be improved by forming the urethane rubber layer to
have a foamed structure or largely lowering the hardness (or
increasing the softness) of the urethane rubber layer. In this
case, however, the urethane elastomer may lose its proper wear
resistance and accordingly its durability.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
composite solid tire that has not only an excellent wear resistance
but also an excellent shock-absorbing or -damping property, and a
method of advantageously producing the same. It is another object
of the present invention to provide advantageous techniques for
renewing a waste solid rubber tire that has been worn to such a
degree that its life expectancy has been fulfilled.
According to the present invention, there is provided a composite
solid tire, wherein an inner layer of the solid tire is formed of a
rubber layer, and an outer layer of the solid tire is formed of a
thermo-setting polyurethane elastomer layer.
According to a preferred feature of the present invention, the
rubber layer is formed of a worn solid rubber tire, wherein the
remaining rubber layer of the worn solid rubber tire has a
pre-determined thickness.
According to another preferred feature of the present invention,
the rubber layer is formed of at least one material, which is
softer than the thermo-setting polyurethane elastomer.
According to a first aspect of the method of the present invention,
there is provided a method of producing a composite solid tire
comprising the steps of providing a rubber layer to be the inner
layer of said tire; applying a primer and an adhesive to an outer
circumferential surface of the rubber layer; and forming an outer
layer by causing raw materials of a thermo-setting polyurethane
elastomer to react and cure by die-casting.
According to a second aspect of the method of the present
invention, there is provided a method of producing a composite
solid tire comprising the steps of cutting an outer circumferential
surface of a remaining rubber layer of a worn solid rubber tire;
applying an adhesive to the cut outer circumferential surface of
the rubber layer; and providing, on the outer circumferential
surface of the rubber layer, a thermo-setting polyurethane
elastomer layer by causing raw materials of a thermo-setting
polyurethane to react and cure.
According to another preferred feature of the present invention,
the composite solid tire producing method is embodied by
introducing the raw materials of the thermo-setting polyurethane
elastomer into a space in a die-casting device, wherein the space
is formed between an inner circumferential surface of an outer die
and an outer circumferential surface of the rubber layer, and the
inner circumferential surface and the outer circumferential surface
are heated in a way that a temperature of the outer circumferential
surface is higher than that of the inner circumferential
surface.
In addition, the polyurethane elastomer layer as the outer layer of
the tread portion of the renewed solid tire does not contain,
unlike common rubber layers, any amounts of carbon black.
Therefore, unlike conventional solid rubber tires, no black marks
of the renewed solid tire (i.e., the tread rubber) are left on the
road surface the tire contacts. Thus, the renewed solid tire is
freed of the problems that the black marks may damage the aesthetic
appearance of the road surface and that scattering of black rubber
powder resulting from wearing of tires may damage a work
environment. Moreover, the rubber layer as the remaining portion of
the worn solid rubber tire is utilized, substantially as it is, as
the inner layer of the tread portion of the renewed solid tire.
Therefore, an amount of consumption of the raw materials of the
polyurethane elastomer can be significantly reduced as compared
with the case where an entirety of the tread portion is constituted
by a polyurethane elastomer layer only. This advantageously
prevents or restrains the cost of the manufacture of the composite
solid tire, which has the above-mentioned excellent features, from
increasing.
According to the preferred features of the present invention, the
rubber layer as the remaining portion of the worn solid rubber tire
is utilized, substantially as it is, as the inner layer of the
tread portion of the renewed solid tire. Therefore, an amount of
consumption of the raw materials of the polyurethane elastomer can
be significantly reduced as compared with the case where an
entirety of the tread portion is constituted by a polyurethane
elastomer layer only. This leads to largely saving the amount of
materials used to renew the worn tread portion of the solid tire.
Moreover, according to the present invention, worn solid rubber
tires can be utilized again as renewed solid tires, the worn solid
rubber tires need not be disposed of, so that the present invention
contributes to overcome the social problem with the disposal of
waste tires.
In the renewed solid tire in accordance with the present invention,
an annular tread portion to be attached to an outer circumferential
portion of a wheel is constituted by the rubber layer that is a
remaining portion of the worn solid rubber tire and has an
appropriate thickness, and the room temperature-setting
polyurethane elastomer layer that is integrally formed on the
rubber layer. Therefore, impacts exerted from road surface to the
tread portion can be effectively absorbed or damped by the rubber
layer as an inner layer of the tread portion, and the outer
polyurethane elastomer layer that provides a contact surface of the
tread portion that contacts the road surface enjoys a proper
excellent wear resistance of the polyurethane elastomer, and
accordingly a significantly improved durability. Thus, the renewed
solid tire can enjoy a significantly increased life expectancy.
In addition, according to the present method of manufacturing the
composite solid tire, the inner layer formed of the rubber layer
and the outer layer formed of the thermo-setting polyurethane
elastomer layer are effectively integrated with each other.
Moreover, by cutting an outer surface of a remaining rubber layer
of a worn solid rubber tire, in which the remaining rubber layer
has a pre-determined thickness, and applying the thermo-setting
polyurethane elastomer to the rubber layer, the worn solid rubber
tire can be advantageously utilized. It is also assured that the
thermo-setting polyurethane elastomer layer and the rubber layer
can be more effectively formed into an integral structure.
In particular, in the above-mentioned preferred features of the
present invention, the raw materials of the thermo-setting
polyurethane elastomer, which are introduced into the die-casting
device, react and cure from a side of the rubber layer, whose
temperature is higher than that of the other side of the rubber
layer. Therefore, the feature, in which the thermo-setting
polyurethane elastomer layer formed on the rubber layer is further
firmly integrated with the rubber layer, is exhibited.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, advantages and technical and
industrial significance of the present invention will be better
understood by reading the following detailed description of
presently preferred embodiments of the invention, when considered
in connection with the accompanying drawings, in which:
FIG. 1 is a side elevational view of a portion of a solid rubber
tire, for explaining respective states of the tire before and after
it is worn;
FIG. 2 is a cross-sectional view of a portion of a worn solid
rubber tire, and a portion of a composite solid rubber tire in
which a thermo-setting polyurethane elastomer layer is formed
integrally with the worn solid rubber tire according to the present
invention;
FIG. 3 is a cross-sectional view for explaining steps of a first
half portion of a composite solid tire producing method in
accordance with the present invention; and
FIG. 4 is a cross-sectional view for explaining steps of a second
half portion of the composite solid tire producing method that
follows the first half portion shown in FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, there will be described in detail preferred
embodiments of the present invention by reference to the
drawings.
FIG. 1 is a side elevation view of a portion of a solid rubber tire
10 that is attached to a vehicle, not shown, and has not been worn,
and a side elevation view of a portion of the same solid rubber
tire 10 whose tread portion 14 has been used and worn. FIG. 1 shows
the worn solid tire, which provides an annular rubber layer, and
which is suitably used for the present invention. More specifically
described, the solid rubber tire 10 is formed, as known in the art,
of a single sort of rubber, or a blend of two or more sorts of
rubbers, that is or are selected from NR, IR, SBR, BR, EPM, EPDM,
IIR, and the like. Generally, the solid rubber tire 10 is formed of
a blend of rubbers including NR or IR as a main component, and is
vulcanized. The solid rubber tire 10 is commercially available as a
so-called solid tire. The solid rubber tire 10 has a generally
annular shape, and an outer circumferential surface of a wheel 18
fixed to an axle shaft of the vehicle is attached to an inner
circumferential portion of the tire 10, by a well known method,
such as bonding, press-fitting, or fitting.
The solid rubber tire 10 has, on a side surface thereof, a tread
wear indicator (or a tire wear indicator) 12 that indicates a limit
of use of the tire 10. The tread wear indicator 12 has, e.g., a
triangular shape and is formed by indent or relief. When the tread
portion 14 of the solid rubber tire 10 is worn little by little
because of repeated friction with road surface and eventually the
outer circumferential surface of the tread portion 14 that contacts
the road surface reaches the tread wear indicator 12, the solid
rubber tire 10, i.e., a worn solid rubber tire 16 should be changed
with a new one, because a life expectancy of the tire 10 has been
fulfilled.
According to the present invention, however, the worn solid rubber
tire 16 whose life expectancy has been fulfilled is used to
advantage. More specifically described, as shown in FIG. 1, the
worn solid rubber tire 16 has, as a remaining portion of the solid
rubber tire 10, a worn rubber layer 20 that remains along the
entire circumference of the wheel 18 and has a pre-determined
thickness corresponding to the tread wear indicator 12. As shown in
FIG. 2, on an outer circumferential surface of the worn rubber
layer 20, a thermo-curing or -setting polyurethane elastomer layer
24 is integrally formed to have a pre-determined thickness and
thereby provide a new tread portion 14. Thus, the worn solid rubber
tire 16 is renovated into a renewed solid tire (composite solid
rubber tire) 26 that can be used again with the vehicle.
The above-indicated polyurethane elastomer layer 24 is integrally
formed on the outer circumferential surface of the worn rubber
layer 20, by casting, into the die-casting device, conventionally
known raw materials of a thermo-curing or -setting polyurethane, so
that the renewed solid rubber tire 26 may have a desired thickness.
Generally, the raw materials of the thermo-setting polyurethane
contain, as a polyisocyanate component, a tolylene diisocyanate
(TDI), a diphenylmethane diisocyanate (MDI), and a naphthalene
diisocyanate (NDI) or the like, and additionally contain, as a
polyol component, a poly(oxybutylene)glycol, polyester polyol,
polyethylene adipate glycol or the like. The raw materials
additionally contain a diamine, a diol or the like, as a catalyst
that causes the polyisocyanate component and the polyol component
to react with each other, and cure, while the raw materials are
heated. The catalyst can be selected, as needed, from various
commercially available products, such as the ones available under
commercial name "Adiprene", "Vibrathane", "Multrathane",
"Vulkollan", "Hiprene", or the like.
The polyurethane elastomer, which forms the layer 24, has an
excellent wear resistance property, as clearly shown in the
following TABLE 1. TABLE 1 compares the comparison of the physical
properties of "Vulkollan", which is an example of the commercially
available elastomers suitable for the present invention, with a
commercially available room temperature-setting polyurethane. In
the present invention, a polyurethane elastomer, whose
characteristic value according to Taber Abrasion Test (DIN 53516)
is 90 mm.sup.3 or less, preferably 70 mm.sup.3 or less, more
preferably 50 mm.sup.3 or less, is advantageously used.
TABLE-US-00001 TABLE 1 Polyurethane elastomer Room Thermo-setting
temperature- Measuring elastomer setting method (VULKOLLAN)
elastomer Hardness DIN 53505 80 80 (Shore hardness A) Tensile
strength (MPa) DIN 53504 35 15 Breaking elongation (%) DIN 53504
800 370 Tear strength (KN/m) DIN 53515 65 24 Impact resilience (%)
DIN 53512 55 35 Wear resistance (mm.sup.3) DIN 53516 40 102
As the polyurethane elastomer, which has the excellent wear
resistance and is used for the polyurethane elastomer layer 24, NDI
elastomer is advantageously used. More specifically described,
naphthalene-1,5-diisocyanate (NDI) is used as a polyisocyanate
component, and polyester polyol or the like is used as a polyol
component. After the two components are reacted with each other, in
advance, so as to form an NDI/ester prepolymer, a glycol
cross-linking agent, etc. are mixed with the prepolymer, and the
resultant mixture is heated, so as to form a desired solid
NDI-based elastomer. Thus, the desired layer 24 is formed by a
die-casting method in which the polyurethane raw materials are cast
into the die-casting device. The raw materials of the polyurethane
elastomer having an excellent wear resistance are commercially
available; for example, polyurethane raw materials available under
commercial name "VULKOLLAN" from Bayer AG, Germany, are
advantageously used.
Generally, it is preferred that the materials of the heat-curing
polyurethane elastomer used to form the polyurethane elastomer
layer 24 be reacted, and cured, at a low heating temperature of,
e.g., from 70.degree. C. to 115.degree. C. This assures that the
curing of polyurethane materials does not need to subject the
rubber layer 20 of the worn solid rubber tire 16 to high
temperatures, thereby effectively preventing the properties of the
rubber layer 20 from being changed by heat. Therefore, the
composite solid rubber tire 26 in which the polyurethane elastomer
layer 24 is integrally formed on the rubber layer 20 can
advantageously exhibit, against shocks or impacts exerted thereto,
the cushioning property of the rubber layer 20. In addition, the
durability of the rubber layer 20 and accordingly the life
expectancy of the renewed solid rubber tire 26 as a whole can be
advantageously improved.
Also, in the renewed solid rubber tire 26 constructed as described
above, an outer circumferential surface of the polyurethane
elastomer layer 24 provides a contact surface that contacts the
road surface. Therefore, the polyurethane elastomer can exhibit its
proper wear resistance, and accordingly the renewed solid rubber
tire 26 can enjoy a significantly improved life expectancy. In
addition, since the rubber layer 20 is present under the
polyurethane elastomer layer 24 having the excellent wear
resistance, the rubber layer 20 can effectively absorb or damp the
impacts transmitted from the road surface to the vehicle, even if a
hardness of the rubber layer 24 may be such a level of Shore
hardness 80 A or over, while an ordinary rubber layer has a Shore
hardness less than 70 A and an ordinary room temperature-setting
elastomer has a Shore hardness less than 80 A. Thus, the rubber
layer 20 largely contributes to improving, e.g., a driving comfort
of the vehicle. In order to advantageously exhibit the effect of
presence of the rubber layer 20, it is preferred that a percentage
of a thickness of the polyurethane elastomer layer 24 relative to a
whole thickness of the renewed solid rubber tire 26 in a radial
direction thereof be not more than 40%, more preferably, not more
than 30%, and that a percentage of a thickness of the rubber layer
20 relative to the whole thickness of the renewed solid rubber tire
26 be not less than 60%.
Moreover, the polyurethane elastomer layer 24 does not contain,
unlike the rubber layer 20, any amounts of carbon black as a
reinforcing material. Therefore, although the renewed solid rubber
tire 26 is rolled and moved on the road surface, no black marks of
the tire 26 are left on the road surface. Thus, the polyurethane
elastomer layer 24 contributes to keeping the environment clean. In
addition, the elastomer layer 24 has no possibilities of damaging a
work environment where the renewed solid rubber tires 26 are
produced.
The renewed solid rubber tire 26 constructed as described above
according to the present invention is produced by a composite solid
tire producing method also according to the present invention. The
composite solid tire producing method is based on a known method,
e.g., a die-casting method. In the composite solid tire producing
method, before the desired thermo-setting polyurethane elastomer
layer 24 is formed, the outer circumferential surface 22 of the
rubber layer 20 of the worn solid rubber tire 16 is worked, i.e.,
cut or machined using, e.g., a lathe so as to remove, from the
rubber layer 20, a superficial portion thereof having a
pre-determined thickness. Thus, oil adhered to the outer surface,
and/or impregnated into, the inner mass, of the rubber layer 20,
and/or particles biting into the outer surface of the same 20 are
removed to assure that the polyurethane elastomer layer 24 can be
more effectively bonded to the clean outer surface 22 of the rubber
layer 20. On the clean outer surface 22 of the rubber layer 20, a
primer layer is formed using a known primer to improve a degree of
bonding of the outer surface 22, and additionally an adhesive layer
is formed, on the primer layer, using a known adhesive suitable for
polyurethanes. Since the primer layer and the adhesive layer are
formed on the outer surface 22 of the rubber layer 20, the
polyurethane elastomer layer 24 can be more firmly bonded to the
rubber layer 20.
After the primer and then the adhesive are applied to the rubber
layer 20, the worn solid rubber tire 16 including the worn rubber
layer 20 is set in an appropriate die-casting device 32.
Subsequently, as shown in FIG. 3, raw materials of a thermo-setting
polyurethane are cast in the die-casting device 32.
More specifically described, as shown in FIG. 3, the die-casting
device 32 includes an outer die 34 having a cylindrical shape and
including a bottom wall, and a core-like inner die 36 that is
provided in an inner space of the outer die 34 such that the inner
die 36 is concentric with the outer die 34. The worn solid rubber
tire 16 is set in the die-casting device 32 such that the inner die
36 fits in an inner bore of the tire 16. It is desirable that at
least the outer die 34 is pre-heated in a suitable furnace at a
pre-determined temperature, for example, at about 100 to
110.degree. C. In this case, it is desirable that the rubber layer
20 of the solid rubber tire 16 is also pre-heated at a temperature
higher than that of the pre-heated outer die 34. For example, it is
preferable that the temperature of the pre-heated solid rubber tire
16 is at least about 5.degree. C. higher than that of the
pre-heated outer die 34. Adaptation of the above-mentioned
relationship between the temperature of the outer layer die 34 and
that of the lubber layer 20 effectively causes the raw materials of
the thermo-setting polyurethane elastomer to react and cure from
the side of the rubber layer 20. As a result, thus formed
polyurethane elastomer layer 24 and the rubber 20 are fixed to each
other, much firmer than layers obtained without the adaptation of
the above-mentioned relationship. Therefore, the solid tire of the
present invention has an advantageously integrated structure.
In this state, a known material casting device 40 casts raw
materials 42 of a room temperature-setting polyurethane, into an
annular space (i.e., a molding space) 38 located between the outer
circumferential surface of the rubber layer 20 of the worn solid
rubber tire 16 and the inner circumferential surface of the outer
die 34, till the annular space 38 is filled with the raw materials.
The material casting device 40 may be one that has a well known
construction; such as a mixing head or a gun-type injector. The
material casting device 40 is supplied with the polyisocynate
component: A, and the polyol component: B, mixed with the curing
agent (i.e., the catalyst) and, after the two components are mixed
uniformly using an appropriate dynamic or static mixer, the mixture
is cast in the die-casting device 32. The polyisocynate component:
A and the polyol component: B may be previously reacted to form a
pre-polymer before being supplied to the material casting device
40. In this case, the material casting device 40 is supplied with
the pre-polymer and the curing agent, and after the two components
are mixed, the mixture is cast in the die-casting device 32.
The polyurethane raw materials 42 cast in the die-casting device 32
react and cure, while they are heated. Thus, the polyurethane
elastomer layer 24 is integrally formed on the outer surface of the
rubber layer 20. Subsequently, as shown in FIG. 4, an integral mold
product 44 including the rubber layer 20 and the polyurethane
elastomer layer 24 is removed from the die-casting device 32, and
is subjected to a finishing operation. More specifically described,
widthwise opposite ends of an outer circumferential surface of the
polyurethane elastomer layer 24 are rounded to provide rounded
portions 46, and are thereby prevented from being chipped off in
use. Thus, a desired renewed solid tire 48 is produced.
In the above-described method of producing the composite solid tire
48, the polyurethane raw materials 42 are just cast in the
die-casting device 32, so as to integrally form the polyurethane
elastomer layer 24 on the outer circumferential surface of the
rubber layer 20. Thus, the composite solid tire 48 can be very
easily produced. In addition, not all portions of the composite
solid tire 48 are formed of the polyurethane elastomer, but just
the polyurethane elastomer layer 24 is integrally formed on the
outer surface of the worn rubber layer 20 remaining with the
pre-determined thickness along the entire circumference of the
wheel 18. Thus, the present composite solid tire producing method
is economical since the amount of use of the polyurethane raw
materials 42 is considerably small.
The composite solid tire 48 produced by the method shown in FIGS. 3
and 4 is attached to the wheel 18, and is used with the vehicle,
such that the wheel 18 is fixed to the inner bore of the tire 48 by
a conventionally known method such as bonding, press-fitting, or
fitting. Thus, the composite solid tire 48 can enjoy the
above-described special advantages of the polyurethane elastomer
layer 24 formed on the rubber layer 20.
In summary, the renewed solid tire in accordance with the present
invention can enjoy a significantly improved life expectancy, and
can exhibit a significantly improved shock absorbing or damping
effect against shocks exerted from road surface to a body of a
vehicle. In addition, no black marks of the tire are left on the
road surface, which largely contributes to keeping an aesthetic
appearance of the environment and improving a work environment. In
addition, since, according to the present invention, worn solid
rubber tires can be utilized again as renewed solid tires, the worn
solid rubber tires need not be disposed of, and the social problem
with the disposal of waste tires can be overcome. While the present
invention has been described in its preferred embodiments, it is to
be understood that the present invention is by no means limited to
the details of those embodiments but may be otherwise embodied.
While the present invention has been described in its preferred
embodiments, it is to be understood that the present invention is
by no means limited to the details of those embodiments but may be
otherwise embodied.
For example, the worn solid tires 16 employed according to the
present invention may be waste solid tires obtained by recovery of
so-called solid rubber tires, i.e., common rubber-based solid tires
that are widely used in forklift trucks, industrial tractors,
battery carriers, trailers, or the like. In addition, the worn
solid tires 16 may be solid tires that are formed of a common solid
rubber and are used as, e.g., wheels of a cart or casters of a
baggage. Moreover, the worn solid tires 16 may be pneumatic-type
solid tires or cylindrical-base-type solid tires, and the present
invention is applicable to the respective solid-rubber portions of
those tires.
In the composite solid tire producing method shown in FIGS. 3 and
4, the worn solid rubber tire 16 is detached from the wheel 18, and
subsequently is set in the die-casting device 32, and then the
polyurethane elastomer layer 24 is integrally formed on the outer
circumferential surface of the rubber layer 20 of the tire 16.
However, it is possible to set, in the die-casting device 32, the
worn solid rubber tire 16 that is not detached from the wheel 18
but remains attached to the wheel 18, and integrally form the
polyurethane elastomer layer 24 on the outer surface of the rubber
layer 20 of the tire 16.
The polyurethane raw materials 42 used to form the polyurethane
elastomer layer 24 do not contain any amounts of carbon black as a
reinforcing material, but may contain one or more known additives
such as a coloring agent to add a desired color to the elastomer
layer 24; an antibacterial agent to give an antibacterial activity
to the layer 24; a photocatalyst; or an ultraviolet-ray absorbing
agent.
In each of the illustrated embodiments, the worn solid tire, to
which the present invention is applicable, is used to produce the
renewed solid tire. However, it is to be understood that the
present invention is by no means limited to the details of those
embodiments but may be otherwise embodied. For example, it is
possible to form a new annular rubber layer for an inner
circumferential portion of the solid tire, and form the
thermo-setting polyurethane elastomer layer having an appropriate
thickness on the outer circumferential surface of the rubber layer,
for thereby obtaining the desired composite solid tire.
It is desirable that the rubber-layer of the above-mentioned
composite solid tire, in which the thermo-setting polyurethane
elastomer layer is formed on the outer circumferential surface of
the rubber layer, is formed of at least one material, which is
softer than the thermo-setting polyurethane elastomer. Generally,
the rubber layer is formed of a rubber, whose hardness (Shore A
hardness) is 70 A or lower. It is also possible to employ a
composite rubber structure, wherein a core is formed of a
relatively soft rubber, and the core is covered by another rubber
layer, which is harder than the core.
It is to be understood that the present invention may be embodied
with other changes, modifications, and improvements that may occur
to a person skilled in the art, without departing from the spirit
and scope of the present invention.
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